Q.

Using a battery, a 100 pF capacitor is charged to 60 V and then the battery is removed. After that, a second uncharged capacitor is connected to the first capacitor in parallel. If the final voltage across the second capacitor is 20 V, its capacitance is (in pF)          [2025]

1 600  
2 200  
3 400  
4 100  

Ans.

(2)

New potential =C0V0C0+C=V03

3C0V0=C0V0+CV0

2C0V0=CV0

C=2C0=2×100=200 pF